In recent years, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a middle or large-sized battery module having a plurality of battery cells electrically connected to each other because high output and large capacity are necessary for the middle or large-sized devices.
Preferably, a middle or large-sized battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell (unit battery) of the middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight, the manufacturing cost of the pouch-shaped battery is low, and it is easy to modify the shape of the pouch-shaped battery.
Battery cells constituting such a middle or large-sized battery module may be secondary batteries which can be charged and discharged. Consequently, a larger amount of heat is generated from such high-output, large-capacity secondary batteries during charge and discharge of the secondary batteries. In particular, the laminate sheet of each pouch-shaped battery widely used in the battery module has a polymer material exhibiting low thermal conductivity coated on the surface thereof with the result that it is difficult to effectively lower overall temperature of the battery cells.
If the heat, generated from the battery module during charge and discharge of the battery module, is not effectively removed from the battery module, the heat accumulates in the battery module with the result that deterioration of the battery module is accelerated. According to circumstances, the battery module may catch fire or explode. For this reason, a battery pack, which is a high-output, large-capacity battery, needs a cooling system to cool battery cells mounted therein.
A battery module mounted in a middle or large-sized battery pack is generally manufactured by stacking a plurality of battery cells with high integration. In this case, the battery cells are stacked with the battery cells arranged at predetermined intervals such that heat generated from the battery cells during charge and discharge of the battery cells can be removed. For example, the battery cells may be sequentially stacked with the battery cells arranged at predetermined intervals without using an additional member. Alternatively, for battery cells having low mechanical strength, one or more battery cells may be mounted in a cartridge and then a plurality of cartridges may be stacked to constitute a battery module. Coolant channels are defined between the stacked battery cells or between the stacked battery modules so that heat accumulated between the stacked battery cells or between the stacked battery modules can be effectively removed.
In this structure, however, a plurality of coolant channels corresponding to a plurality of battery cells are needed with the result that the overall size of the battery module is increased.
In addition, when a plurality of battery cells is stacked, a plurality of parts related to a cooling structure is further included with the result that the volume of the battery module is increased. Furthermore, a manufacturing process of the battery module is complicated and, therefore, manufacturing cost of the battery module is also greatly increased.